How to use jQuery to call an ASP.NET web service?

I'm trying to use jQuery to get data from an ASP.NET web service (SharePoint Server 2007 lists.asmx), but any call to a web service will really help as a first step in that direction.

I use this method as a wrapper so that I can send parameters. Also using the variables in the top of the method allows it to be minimized at a higher ratio and allows for some code reuse if making multiple similar calls.

function InfoByDate(sDate, eDate){
    var divToBeWorkedOn = "#AjaxPlaceHolder";
    var webMethod = "http://MyWebService/Web.asmx/GetInfoByDates";
    var parameters = "{'sDate':'" + sDate + "','eDate':'" + eDate + "'}";

    $.ajax({
        type: "POST",
        url: webMethod,
        data: parameters,
        contentType: "application/json; charset=utf-8",
        dataType: "json",
        success: function(msg) {
            $(divToBeWorkedOn).html(msg.d);
        },
        error: function(e){
            $(divToBeWorkedOn).html("Unavailable");
        }
    });
}

I hope that helps.

Please note that this requires the 3.5 framework to expose JSON webmethods that can be consumed in this manner.

Here is an example to call your webservice using jQuery.get:

$.get("http://domain.com/webservice.asmx", { name: "John", time: "2pm" },
  function(data){
    alert("Data Loaded: " + data);
  });

In the example above, we call "webservice.asmx", passing two parameters: name and time. Then, getting the service output in the call back function.

I don't know about that specific SharePoint web service, but you can decorate a page method or a web service with <WebMethod()> (in VB.NET) to ensure that it serializes to JSON. You can probably just wrap the method that webservice.asmx uses internally, in your own web service.

Dave Ward has a nice walkthrough on this.

$.ajax({
 type: 'POST',
 url: 'data.asmx/getText',
 data: {'argInput' : 'input arg(s)'},
 complete: function(xData, status) {
 $('#txt').html($(xData.responseXML).text()); // result
 }
});

I have a decent example in jQuery AJAX and ASMX on using the jQuery AJAX call with asmx web services...

There is a line of code to uncommment in order to have it return JSON.

SPServices is a jQuery library which abstracts SharePoint's Web Services and makes them easier to use

It is certified for SharePoint 2007

The list of supported operations for Lists.asmx could be found here

Example

In this example, we're grabbing all of the items in the Announcements list and displaying the Titles in a bulleted list in the tasksUL div:

<script type="text/javascript" src="filelink/jquery-1.6.1.min.js"></script>
<script type="text/javascript" src="filelink/jquery.SPServices-0.6.2.min.js"></script>
<script language="javascript" type="text/javascript">

$(document).ready(function() {
  $().SPServices({
    operation: "GetListItems",
    async: false,
    listName: "Announcements",
    CAMLViewFields: "<ViewFields><FieldRef Name='Title' /></ViewFields>",
    completefunc: function (xData, Status) {
      $(xData.responseXML).SPFilterNode("z:row").each(function() {
        var liHtml = "<li>" + $(this).attr("ows_Title") + "</li>";
        $("#tasksUL").append(liHtml);
      });
    }
  });
});
</script>
<ul id="tasksUL"/>

I quite often use ajaxpro along with jQuery. ajaxpro lets me call .NET functions from JavaScript and I use jQuery for the rest.